1. Field of the Invention
This invention relates to a method for making a metal-oxide-semiconductor (MOS) device, more particularly to a method involving formation of a hydrogen-passivated polycrystalline titanium dioxide film on a semiconductor substrate.
2. Description of the Related Art
A metal oxide semiconductor (MOS) device, such as MOS capacitors and transistors, includes an insulator film sandwiched between an electrode layer and a semiconductor substrate. Conventionally, the insulator film is made from silicon dioxide. With rapid integration of elements and scale down of the MOS devices, the silicon dioxide film is required to be thinned to a considerable extent, and the area thereof is required to be smaller and smaller. However, when the thickness of the silicon dioxide film is below 2.5 nm, the likelihood of current leakage is relatively high due to direct tunneling effect. In addition, it is also an issue on how to maintain the desired capacitance when the area of the silicon dioxide film is further reduced. In order to overcome the aforesaid drawbacks, a high dielectric constant material, such as titanium dioxide, has been proposed heretofore to replace silicon dioxide. Conventionally, a polycrystalline titanium dioxide film is formed using metal organic chemical vapor deposition (MOCVD) techniques. However, the performance of a MOSFET device with the titanium dioxide film is relatively poor due to the presence of a large number of defects, such as grain boundary defects, interface traps, oxide traps, and oxygen vacancies, in the polycrystalline titanium dioxide film, and a relatively low energy barrier height for the titanium dioxide, which can result in severe current leakage.